Location measuring method and apparatus using access point for wireless local area network service

ABSTRACT

Measuring a location of a communication terminal using a wireless local area network access point based on location coordinates of the access points and global positioning system (GPS) location information of the communication terminal.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims priority from Korean Patent Application No.10-2010-0121494, filed on Dec. 1, 2010, in the Korean IntellectualProperty Office, the disclosure of which is incorporated herein byreference in its entirety.

BACKGROUND

1. Field

Exemplary embodiments relate to a technique for measuring a location ofa communication terminal, and more particularly, to a location measuringmethod and apparatus using an access point for a wireless local areanetwork (WLAN) service.

2. Description of the Related Art

With the development of mobile communication techniques, studies havebeen actively made on location measuring techniques that measure alocation of a mobile terminal in a communication network. Typically, aglobal positioning system (GPS)-based location measuring technique usingsatellites has been widely used.

The GPS-based location measuring technique has a disadvantage of havingto mount a GPS receiver on a mobile terminal. Also, because theGPS-based location measuring technique was developed by the U.S.Department of Defense for military use, a high-precision GPS-basedlocation measuring technique is not disclosed. Furthermore, theGPS-based location measuring technique has limited use since thetechnique is useless in buildings, for example, houses, offices, orshops, where satellite signals cannot be received. To overcome thesedrawbacks, attempts have been made to measure a location of a terminalusing an access point for a WLAN service.

The WLAN service enables users of mobile terminals to wirelessly connectto the Internet through a WLAN access point near the mobile terminals,for example, notebook computers, personal digital assistants (PDAs),smart phones, and the like, that have WLAN cards mounted therein.Recently, to meet the increasing demand for the WLAN service,installation of access points in buildings, such as large-scaledshopping malls, and the like, has increased.

Since many access points have now been installed in buildings, alocation of a mobile terminal can be measured in buildings where aGPS-based location measuring technique cannot be applied by using theaccess points.

Accordingly, research and development on a location measuring techniqueusing an access point for a WLAN service has recently been flourishing.

SUMMARY

Aspects of the exemplary embodiments are directed to providing alocation measuring method and apparatus for measuring a location of acommunication terminal using an access point for a wireless local areanetwork (WLAN) service.

Also, the exemplary embodiments are directed to providing a locationmeasuring method and apparatus for measuring a location of acommunication terminal using an access point for a WLAN service, inwhich a location coordinate is corrected using global positioning system(GPS) location information, thereby improving the precision in locationmeasurement.

Additional aspects will be set forth in the following description, andin part will be even more apparent from the exemplary embodiments setforth.

In one aspect of the exemplary embodiments, a method of measuring alocation of a communication terminal using an access point may includestoring location coordinates of a plurality of access points in astorage unit, receiving from the communication terminal globalpositioning system (GPS) location information of the communicationterminal, extracting the location coordinates from the storage unit,calculating the location of the communication terminal using theextracted location coordinates, and correcting the calculated locationusing the GPS location information, as a final location coordinate ofthe communication terminal.

The correcting may comprise selecting a correction ratio based on anumber of the plurality of access points, and determining, as the finallocation coordinate of the communication terminal, a location betweenthe GPS location information and the calculated location according tothe correction ratio.

Preferably, the selecting of the correction ratio may comprise selectingthe correction ratio based on the number of the plurality of accesspoints and a precision of the GPS location information.

The method may further comprise, receiving from the communicationterminal signal strengths of signals received by the communicationterminal from the plurality of access points and calculating an errorradius based on an average of the signal strengths.

The calculating may comprise selecting from among the plurality ofaccess points nearby access points nearest to the communication terminalbased on the location coordinates stored in the storage unit and the GPSlocation information of the communication terminal, extracting alocation coordinates of the nearby access points from the storage unit,calculating a barycentric coordinate using the extracted locationcoordinates of the nearby access points, and determining the calculatedbarycentric coordinate as the location of the communication terminal.

In another aspect of the exemplary embodiments, an apparatus formeasuring a location of a communication terminal may include a storageunit that stores location coordinates of a plurality of access points, areceiver that receives from the communication terminal globalpositioning system (GPS) location information of the communicationterminal, and a location determining unit that extracts the locationcoordinates from the storage unit, calculates the location of thecommunication terminal using the extracted location coordinates, andcorrects the calculated location using the GPS location information as afinal location coordinate of the communication terminal.

The location determining unit may determine, as the final locationcoordinate of the communication terminal, a location between the GPSlocation information and the calculated location according to correctionratio determined based on a number of the plurality of access points.

Preferably, the location determining unit may select the correctionratio based on the number of the plurality of access points and aprecision of the GPS location information.

The location determination unit may further calculate an allowable errorradius based on an average of signal strengths of signals received bythe communication terminal from the plurality of access points.

Also, the location determining unit may calculate a barycentriccoordinate using the location coordinates, and may determine thecalculated barycentric coordinate as the location coordinate of thecommunication terminal.

DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagram illustrating a communication environment accordingto an exemplary embodiment.

FIG. 2 is a block diagram illustrating a network structure of a locationmeasuring system according to an exemplary embodiment.

FIG. 3 is a diagram illustrating the collection of access pointinformation for a location according to an exemplary embodiment.

FIG. 4 is a table of access point information for locations according toan exemplary embodiment.

FIG. 5 is a flowchart illustrating a process for determining a locationcoordinate of an access point in a location measuring server accordingto an exemplary embodiment.

FIG. 6 is a graph illustrating an example of the extraction of a risingpoint of inflection based on a signal strength distribution of an accesspoint over time according to an exemplary embodiment.

FIG. 7 is a flowchart illustrating a process for measuring a location ofa communication terminal in a location measuring server according to anexemplary embodiment.

FIG. 8 is a flowchart illustrating a process for measuring a location ofa communication terminal in a location measuring server according toanother exemplary embodiment.

FIG. 9 is a flowchart illustrating a process for calculating a locationcoordinate using the barycentric method according to an exemplaryembodiment.

FIG. 10 is a diagram illustrating the calculation of a barycentriccoordinate according to an exemplary embodiment.

FIG. 11 is a block diagram illustrating a structure of a locationmeasuring server according to an exemplary embodiment.

FIG. 12 is a diagram illustrating an example of a location coordinatecorrection ratio according to an exemplary embodiment.

Throughout the drawings and the detailed descriptions, unless otherwisedescribed, the same drawing reference numerals will be understood torefer to the same elements, features, and structures. The relative sizeand depiction of these elements may be exaggerated for clarity,illustration, and convenience.

DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS

The following detailed descriptions are provided to assist the reader ingaining a comprehensive understanding of the methods, apparatuses,and/or systems described herein. Accordingly, various changes,modifications, and equivalents of the systems, apparatuses and/ormethods described herein will be suggested to those of ordinary skill inthe art. Also, descriptions of well-known functions and constructionsmay be omitted for increased clarity and conciseness.

FIG. 1 is a diagram illustrating a communication environment accordingto an exemplary embodiment.

Referring to FIG. 1, the communication environment includes basestations (A, B, C) of the Global System for Mobile Communications (GSM)(also known as Node Bs of the Universal Mobile Telecommunications System(UMTS)) that provide a mobile communication service, and access points(APs) that provide an Internet service using a wireless local areanetwork (WLAN) system, for example, Wireless Fidelity (WiFi), in anoverlapping arrangement. A communication terminal may use variousservices including voice communication and wireless Internet servicesvia the base station when the communication terminal is mobile. Also,the communication terminal may use an Internet service by connecting toa wired Internet network via the access point.

Generally, the base station has coverage of several kilometers to tensof kilometers in radius, while the access point providing a WLAN servicehas coverage of only several meters in radius. Due to the low costs forpurchasing and installing the access points, they are installed in largenumbers at various places such as houses, offices, shopping malls, andthe like.

As shown in FIG. 1, a plurality of access points 160-1, . . . , 160-5are placed within respective coverage areas 110, 130, and 150 of basestations. Communication terminal users use an Internet service via theaccess point 160-1, . . . , 160-5 at locations where a signal of theaccess point 160-1, . . . , 160-5 is detected by the communicationterminal. Also, where a signal of the access point 160-1, . . . , 160-5is not detected, the communication terminal users use an Internetservice via a connection to at least one of the base stations orsatellite 170.

Recently, with the advancement of smart phone functions, the number ofsmart phone users is increasing. To provide a high-speed Internetservice to smart phones, the number of access points installed is alsoincreasing. As many access points are particularly installed in placeswith a large floating population, the use of the access points inlocation measurement is increasing. The accuracy of location measurementusing an access point with a narrow coverage is higher than that of abase station with a wide coverage.

FIG. 2 is a block diagram illustrating a network structure of a locationmeasuring system according to an exemplary embodiment.

Referring to FIG. 2, the network may include access points (APs) 290-1,. . . , 290-N providing a WLAN service and base stations 200-1, . . . ,200-N providing a mobile communication service. As shown in FIG. 1, thecoverage of the access points 290-1, . . . , 290-N and the coverage ofthe base stations 200-1, . . . , 200-N may overlap. As the geographiccoverage of the base stations is large, a plurality of access points maybe placed within the coverage of one base station, and one access pointmay be located within coverage areas of multiple base stations.

The access points 290-1, . . . , 290-N are connected to a wired Internetnetwork 210 to provide an Internet service. The base stations 200-1, . .. , 200-N are connected to a mobile communication network 230 to providea mobile communication service. The wired Internet network 210 and themobile communication network 230 are linked to each other. Referring toFIG. 2, the location measuring system includes a location measuringserver 250 connected to the wired Internet network 210 and the mobilecommunication network 230, and an access point information DB 270managed by the location measuring server 250.

The access point information DB 270 stores identity information (forexample, MAC (Media Access Control) address, SSID (Service SetIDentifier), and the like) of access points installed indoors/outdoorsof buildings and location coordinate information that identifies wherethe access points are installed. Also, the access point information DB270 stores access point information for a location that is collected byan access point information collecting terminal while the access pointinformation collecting terminal is mobile. The access point informationfor a location includes collection location information collected by theaccess point information collecting terminal at a predetermined timecycle while the access point information collecting terminal is mobile,identity information and signal strength of access points detected atthe collection locations, and identity information of base stations. Amore detailed description will follow later.

When the location measuring server 250 is receives a request to measurea location of a specific communication terminal, the location measuringserver 250 measures a location of the communication terminal usingidentity information of a base station 200-1, . . . , 200-N in thevicinity of the communication terminal and identity information of anaccess point 290-1, . . . , 290-N to which the communication terminal isconnected. A method of the location measuring server 250 measuring alocation is described in detail below.

FIG. 3 is a diagram illustrating the collection of access pointinformation for a location according to an exemplary embodiment.

As shown in FIG. 3, an access point information collecting terminalmounted in a vehicle 310 collects information by detecting signals fromnearby access points at a predetermined time cycle while the vehicle 310is running. The information collected by the access point informationcollecting terminal includes collection time, collection locationinformation (for example, latitude/longitude), identity information (forexample, MAC address) and signal strength (for example, RSSI (ReceivedSignal Strength Indication)) of an access point which transmits a signaldetected at a collection location, and identity information (cell ID orPN (Pseudo Noise) code) of a base station having a coverage area overthe corresponding collection location.

Referring to FIG. 3, taking point A as an example, the access pointinformation collecting terminal mounted in the vehicle 310 collectsinformation of an access point which transmits a signal detected at thepoint A. The access point information collecting terminal collectslatitude/longitude information of the point A, collection time, MACaddress and signal strength (RSSI) of the access point which transmitsthe signal detected at the point A, and identity information of a basestation which covers the point A. As described above, the access pointinformation collecting terminal collects information of access pointsdetected at every point (A, B, C . . . ) at a predetermined time cycle(for example, every minute) while the vehicle is running.

FIG. 4 is a table of access point information for locations according toan exemplary embodiment. As described above with reference to FIG. 3,the access point information collecting terminal collects information ofnearby access points at a predetermined time cycle while running, andthe collected access point information for location is shown in FIG. 4.As shown in FIG. 4, the table has a time field 410, a location field430, a MAC address filed 450, an RSSI field 470, and a cell ID field490.

The time field 410 records the time at which the access pointinformation collecting terminal collects information of an access point.The location field 430 records collection location information(latitude/longitude information) of the access point informationcollecting terminal at the time at which the information of the accesspoint is collected. The MAC address filed 450 records a MAC address ofan access point detected at a collection location. The RSSI field 470records a strength of a signal received from an access point detected ata collection location. The cell ID field 490 records a cell ID of a basestation covering a collection location of the access point informationcollecting terminal at the time at which the information of the accesspoint is collected. Although FIG. 4 shows only one cell ID for a basestation being recorded, a plurality of cell IDs detected at the cellboundary may be recorded.

To measure a location of a communication terminal using an access point,the location measuring method according to the exemplary embodimentemploys installation location coordinates (or actual geographicallocation coordinates) where access points are physically installed.Generally, the access points 160 installed by communication serviceproviders have their installation location coordinates given by thecommunication service providers. However, a personal access pointinstalled by a local user (for example an access point located within aresidence) may not be reported to the communication service providers.Accordingly, an installation location coordinate of the personal accesspoint is not known unless the installation location coordinate isidentified by an installer. Accordingly, there is a need to estimate aninstallation location coordinate of an access point of which theinstallation location coordinate is not identified among access pointsof which information is collected by the access point informationcollecting terminal while the access point information collectingterminal is mobile, as described above with reference to FIG. 3.

Hereinafter, a process for estimating an installation locationcoordinate (or an actual location coordinate) of an access point, ofwhich the installation location coordinate is not identified, amongaccess points of which information is collected by the access pointinformation collecting terminal while the access point informationcollecting terminal is mobile, is described with reference to FIG. 5.That is, an estimated installation location coordinate of an accesspoint is a location coordinate of the access point determined based onan estimated value, but not an actual location coordinate of the accesspoint.

FIG. 5 is a flowchart illustrating a process for determining a locationcoordinate of an access point in a location measuring server accordingto an exemplary embodiment.

Referring to FIG. 5, the access point information collecting terminalcollects information by detecting signals from nearby access points at apredetermined time, as described above with reference to FIGS. 3 and 4.The access point information for location collected by the access pointinformation collecting terminal may be transmitted to the locationmeasuring server 250 via the Internet network 210 or the mobilecommunication network 230. The location measuring server 250 stores thereceived access point information for location in the access pointinformation DB 270. Alternatively, the access point information forlocation collected by the access point information collecting terminalmay be stored in the access point information DB 270 by an operator.

After the access point information for location is collected, thelocation measuring server 250 extracts, from the access pointinformation DB 270, collection information for location of a specificaccess point, of which an installation location coordinate (or an actuallocation coordinate) is not identified, among the collected access pointinformation for location (S501). That is, the location measuring server250 extracts collection information for locations including informationof the specific access point. For example, when a MAC address is‘111.112’, as shown in FIG. 4, the location measuring server 250extracts information of Group 1, Group 2, Group 3, Group 4, and GroupN−1 including MAC address ‘111.112’.

After the collection information for location of the specific accesspoint is extracted, as described above, the location measuring server250 extracts the signal strength (for example, RSSI) among thecollection information for locations and chronologically arranges theextracted signal strength in the order of measurement time (S503). Forexample, referring to FIG. 4, the time sequential arrangement of thesignal strength of the access point including MAC address ‘111.112’ is−40 dB, −50 dB, −80 dB, −80 dB, −40 dB, and −40 dB.

After the location measuring server 250 chronologically arranges thesignal strength of the specific access point, the location measuringserver 250 extracts a rising point of inflection by analyzing thechanges in the signal strength over time (S505). Here, the rising pointof inflection is a point where the signal strength rises and reaches thehighest. Specifically, FIG. 6 shows an example of the extraction of arising point of inflection based on a signal strength distribution overtime. As shown in FIG. 6, when the signal strength of the access pointis arranged in the order of time, the points A and C are where thesignal strength rises and reaches the highest, and thus, are extractedas rising points of inflection.

After the rising points of inflection are extracted as described above,the location measuring server 250 calculates a barycentric coordinate ofa polygon (or a straight line) by using the apices of collectionlocation coordinates of the rising points of inflection. The locationmeasuring server 250 determines the calculated barycentric coordinate asan imaginary location coordinate of the specific access point, andstores the imaginary location coordinate in the access point informationDB 270 as the estimated location of the access point (S507). Here, thebarycentric coordinate may be replaced by the incenter, thecircumcenter, and the like. Also, the barycentric coordinate may beadjusted by applying a weight to the signal strength.

In this exemplary embodiment, the rising point of inflection is usedbecause the rising point of inflection is a point where the signalstrength of an access point is highest, and thus is closest to alocation where the access point is actually installed.

The process for determining an imaginary location coordinate of anaccess point as described with reference to FIG. 5 is performed on allaccess points, of which installation location coordinates (or actuallocation coordinates) are not identified, among the access pointscollected by the access point information collecting terminal while theaccess point information collecting terminal is mobile.

FIG. 7 is a flowchart illustrating a process for measuring a location ofthe communication terminal in the location measuring server 250according to an exemplary embodiment.

Referring to FIG. 7, the location measuring server 250 receives, from aspecific communication terminal to be measured for a location of thecommunication terminal, information for location measurement including,for example, information of access points and global positioning system(GPS) location information collected by the communication terminal(S701).

After the location measuring server 250 receives the information forlocation measurement from the specific communication terminal, thelocation measuring server 250 checks whether information of an accesspoint is included in the information for location measurement (S703).When information of an access point is not included in the informationfor location measurement, the location measuring server 250 returns anerror message (S705). The error message is transmitted to an object thathas requested location measurement, for example, the specificcommunication terminal if the location measurement request is receivedfrom the specific communication.

On the contrary, when information of an access point is included in theinformation for location measurement, the location measuring server 250checks whether information of at least two access points is included(S707). When information of one access point is included, the locationmeasuring server 250 extracts an imaginary location coordinate of thecorresponding access point from the access point information DB 270(S709). The imaginary location coordinate is described above withreference to FIG. 5. When the access point does not have an imaginarylocation coordinate, the location measuring server 250 may extract acollection location coordinate where the highest signal strength isdetected, among collection location coordinates at which information ofthe corresponding access point is collected.

When information of at least two access points is included, the locationmeasuring server 250 calculates a location coordinate of thecommunication terminal using the corresponding access points (S711). Aprocess for calculating a location coordinate of a communicationterminal using at least two access points is described below withreference to FIG. 8.

After the location measuring server 250 calculates the locationcoordinate in S709 or S711, the location measuring server 250 checkswhether GPS location information is included in the information forlocation measurement received in S701 (S713). When GPS locationinformation is not included, the location measuring server 250 transmitsthe location coordinate calculated in S709 or S711 to an object that hasrequested location measurement, for example, the specific communicationterminal if the location measurement request is received from thespecific communication terminal.

On the contrary, when GPS location information is included, the locationmeasuring server 250 corrects the location coordinate calculated in S709or S711 using the GPS location information (S715). That is, the locationmeasuring server 250 corrects the location coordinate calculated in S709or S711 towards the GPS location coordinate.

Specifically, the location measuring server 250 corrects the locationcoordinate based on the number of access points included in theinformation for location measurement received in S701. FIG. 12illustrates an example of a location coordinate correction ratio. Asshown in FIG. 12, the greater the number of access points used forlocation measurement or the greater the precision of the GPS locationinformation, the more the location coordinate calculated in S709 or S711may be corrected towards the GPS location coordinate. For example, whenthe number of access points is nine and the precision of the GPS is 35meters or more, a correction ratio is 1:2. That is, a location where astraight line connecting the location coordinate calculated in S709 orS711 and the GPS location coordinate is divided into 1:2 is determinedas a final location coordinate.

After the location measuring server 250 corrects the location coordinatecalculated in S709 or S711 using the GPS location coordinate, asdescribed above, the location measuring server 250 transmits thecorrected, final location coordinate to an object that has requestedlocation measurement, for example, the specific communication terminalif the location measurement request is received from the specificcommunication terminal (S717).

Additionally, after the location measuring server 250 calculates thefinal location coordinate as described with reference to FIG. 7, thelocation measuring server 250 may calculate an allowable error inradius. That is, the location measuring server 250 may calculate anallowable error radius relative to the final location coordinate.Specifically, the location measuring server 250 may calculate anallowable error radius based on an average of the signal strength ofaccess points used in measuring the location coordinate by the processof FIG. 7 and whether a GPS location coordinate is reflected. Thecalculation equation may be as follows:

When GPS Location Coordinate is Reflected

(1) When RSSI_AVERAGE is higher than −90Radius=(INT)(|(RSSI_AVERAGE+WPS_FACTOR_POINT)|)*GPS_BASE_VALUE

(2) When RSSI_AVERAGE is between −90 and −95 (not including −95)Radius=(INT)(|(RSSI_AVERAGE+WPS_FACTOR_POINT)|)*GPS_BASE_VALUE

(3) When RSSI_AVERAGE is −95 or lowerRadius=(INT)(|(RSSI_AVERAGE+WPS_FACTOR_POINT)|)*GPS_BASE_VALUE

When GPS Location Coordinate is not Reflected

(1) When RSSI_AVERAGE is higher than −90Radius=(INT)(|(RSSI_AVERAGE+WPS_FACTOR_POINT)|)*WPS_BASE_VALUE

(2) When RSSI_AVERAGE is between −90 and −95 (not including −95)Radius=(INT)(|(RSSI_AVERAGE+WPS_FACTOR_POINT)|)*WPS_(—)90_VALUE

(3) When RSSI_AVERAGE is −95 or lowerRadius=(INT)(|(RSSI_AVERAGE+WPS_FACTOR_POINT)|)*WPS_(—)95_VALUE

Here, ‘RSSI_AVERAGE’ is an average of the signal strength of accesspoints used for location measurement, and ‘WPS_FACTOR_POINT’ is a basevalue of signal strength and in this embodiment, is set as −40 dB. Also,‘GPS_BASE_VALUE’, ‘WPS_BASE_VALUE’, ‘WPS_(—)90_VALUE’, and‘WPS_(—)95_VALUE’ are each a correction coefficient, and‘GPS_BASE_VALUE’ is smaller than ‘WPS_BASE_VALUE’ because the precisionin location measurement is improved when a GPS location coordinate isreflected. Also, ‘WPS_BASE_VALUE’<‘WPS_(—)90_VALUE’<‘WPS_(—)95_VALUE’.‘GPS_BASE_VALUE’ may vary depending on the precision in the GPS locationcoordinate.

Hereinafter, the above step S711 of FIG. 7, that is, a process forcalculating a location coordinate using nearby access points isdescribed in detail with reference to FIGS. 8 and 9.

FIG. 8 is a flowchart illustrating a process for measuring a location ofa communication terminal in the location measuring server 250 accordingto another exemplary embodiment.

Referring to FIG. 8, the location measuring server 250 first selectsaccess points having an installation location coordinate (or an actuallocation coordinate) among the nearby access points, of whichinformation is received from the specific communication terminal (S801).That is, the location measuring server 250 checks whether there is anaccess point having an actual location coordinate stored in the accesspoint information DB 270, using identity information (for example, MACaddress) of the nearby access points. Assume that the number of theselected access points is ‘n’.

In this instance, when there is no access point having an actuallocation coordinate, an access point is not selected in this step. Whenselecting an access point having an actual location coordinate, only anaccess point having a predetermined signal strength or higher may beselected. A low signal strength may be interpreted as being located at adistance away from the communication terminal, and accordingly, anaccess point having a low signal strength is not selected even thoughits actual location coordinate exists.

Next, the location measuring server 250 selects the top k access pointsbased on signal strength among access points excluding access pointshaving an actual location coordinate (S803). For example, when there aresix access points having an actual location coordinate among thirtynearby access points, of which information is received from the specificcommunication terminal, the location measuring server 250 selects thetop k access points having high signal strength among twenty four accesspoints.

Here, R=(k+n) is preferably L^(i) where L is a natural number of 3 ormore and ‘i’ is a natural number of 2 or more. When the number n ofaccess points having an actual location coordinate is R in S801, thisstep S803 may be omitted.

Next, the location measuring server 250 extracts location coordinates ofthe selected R access points from the access point information DB 270(S805).

Specifically, for access points having an actual location coordinate,the location measuring server 250 extracts their actual locationcoordinates from the access point information DB 270.

For access points not having an actual location coordinate, the locationmeasuring server 250 checks whether their imaginary location coordinatesare stored in the access point information DB 270, and if so, extractsthe imaginary location coordinates from the access point information DB270.

For access points not having an actual location coordinate and animaginary location coordinate, the location measuring server 250extracts collection location coordinates of the top ‘i’ (‘i’ is thenumber of access points) access points having high signal strength fromthe access point information DB 270 based on signal strength forlocation of the corresponding access points detected at each collectionlocation, as location coordinates of the corresponding access points.

For example, when there are three access points not having an actuallocation coordinate and an imaginary location coordinate in which thesignal strength for location of access point A is −40 dB and −50 dB,that of access point B is −50 dB, −60 dB, and −70 dB, and that of accesspoint C is −60 dB and −100 dB, the top three signal strengths are −40 dBand −50 dB of the access point A and −50 dB of the access point B. Thelocation measuring server 250 extracts collection location coordinateswhere −40 dB and −50 dB of the access point A and −50 dB of the accesspoint B are collected, as location coordinates of the access points nothaving an actual location coordinate and an imaginary locationcoordinate.

After the location coordinates of the access points selected in S801 andS803 are extracted as described above, the location measuring server 250calculates a final location coordinate using the extracted locationcoordinates by the barycentric method (S807). The calculating of alocation coordinate using the barycentric method is described in detailwith reference to FIG. 9.

FIG. 9 is a flowchart illustrating a process for calculating a locationcoordinate using the barycentric method according to an exemplaryembodiment.

As shown in FIG. 9, the location measuring server 250 groups the accesspoints extracted in S805 of FIG. 8 into a predetermined number ofgroups, in which M (M is a natural number of 3 or more, and ispreferably equal to L) access points are selected in each group (S901),and calculates a barycentric coordinate of each group using locationcoordinates of access points in each group (S903).

The detailed description is made with reference to FIG. 10. FIG. 10 is adiagram illustrating the calculation of a barycentric coordinateaccording to an exemplary embodiment. In the embodiment described withreference to FIG. 8, R is 9 and M is 3. In S805, when nine access pointsare selected, the selected nine access points are grouped into threegroups, in which three access points are randomly selected in eachgroup. As shown in FIG. 10( a), a barycentric coordinate of a triangleis calculated, the triangle having location coordinates (actual locationcoordinates or imaginary location coordinates) of three access points ineach group as the apices. In FIG. 10( a), ‘A’, ‘B’, and ‘C’ are each abarycentric coordinate of a respective group.

Preferably, access points having an actual location coordinate areequally distributed to each group. For example, when there are threeaccess points having an actual location coordinate, one access pointhaving an actual location coordinate is included in each group. This isto reduce an error in location measurement by including an actuallocation coordinate in each group because the actual location coordinateis a location where an access point is actually installed.

Next, after the barycentric coordinates are calculated, as describedabove, the location measuring server 250 groups the calculatedbarycentric coordinates into a predetermined number of groups, in whichM barycentric coordinates are randomly selected in each group, andre-calculates a barycentric coordinate of each group. This process isrepeated until one barycentric coordinate is obtained (S905).

Specifically, in FIG. 10( a), the calculated barycentric coordinates are‘A’, ‘B’, and ‘C’. Because three barycentric coordinates are sufficientto form a group, further grouping is not necessary. When a barycentriccoordinate of a triangle having the three barycentric coordinates as theapices is calculated, one final barycentric coordinate 1010 is obtainedas shown in FIG. 10( b).

Finally, the location measuring server 250 determines one finalbarycentric coordinate 810 obtained by the barycentric method as a finallocation of the communication terminal (S907).

This embodiment is described based on that R is L^(i). This is because apolygon (for example, a triangle) of the same pattern is used tocalculate a barycentric coordinate in S903 and S905 when M is set toequal L. However, R does not need to equal L^(i). In S903 and S905 forcalculating a barycentric coordinate by grouping, when a number X(M<X<2×M) of barycentric coordinates remain at the end, a finalbarycentric coordinate may be calculated by forming a polygon having thenumber X (M<X<2×M) of barycentric coordinates as the apices.Alternatively, a final barycentric coordinate may be calculated bygrouping the number of barycentric coordinates into a predeterminednumber of groups, in which the number of barycentric coordinates in eachgroup may not be equal.

The embodiment described with reference to FIGS. 8 and 9 is describedbased on nine nearby access points or more. However, in the case of twoor three nearby access points, a barycentric coordinate of the two orthree nearby access points is determined as a final location coordinateof the communication terminal. In the case of four nearby access points,a barycentric coordinate of three access points among the four nearbyaccess points is calculated first, then a barycentric coordinate of thecalculated barycentric coordinate and a location coordinate of the otherone access point is calculated and determined as a final locationcoordinate of the communication terminal. As described above, when thenumber of nearby access points is nine or less, proper grouping of theaccess points and calculating of a barycentric coordinate may beperformed to obtain a final one location coordinate.

FIG. 11 is a block diagram illustrating a structure of the locationmeasuring server 250 according to an exemplary embodiment.

Referring to FIG. 11, the location measuring server 250 according to anexemplary embodiment includes an access point information collectingunit 1110, an imaginary location coordinate determining unit 1130, alocation information request receiving unit 1150, an access pointselecting unit 1170, and a location calculating unit 1190.

The access point information collecting unit 1110 receives access pointinformation for locations collected by the access point informationcollecting terminal at a predetermined time cycle, and stores the accesspoint information for location in the access point information DB 270.The access point information collecting unit 1110 may directly receiveaccess point information for location from the access point informationcollecting terminal via the Internet network 210 or the mobilecommunication network 230. An example of the access point informationfor location is shown in FIG. 4.

The imaginary location coordinate determining unit 1130 estimates anddetermines an installation location coordinate of an access point nothaving an installation location coordinate based on the access pointinformation for location collected by the access point informationcollecting unit 1110. The location coordinate estimated and determinedby the imaginary location coordinate determining unit 1130 is defined asan imaginary location coordinate.

Specifically, the imaginary location coordinate determining unit 1130extracts, from the access point information DB 270, collectioninformation for location of a specific access point, of which an actuallocation coordinate is not identified, among the collected access pointinformation for location. Also, after the imaginary location coordinatedetermining unit 1130 extracts the collection information for locationof the specific access point, the imaginary location coordinatedetermining unit 1130 extracts the signal strength (for example, RSSI)among the collection information for location, chronologically arrangesthe extracted signal strength, and analyzes the changes in the signalstrength over time to extract a rising point of inflection. Here, therising point of inflection is a point where the signal strength risesand reaches the highest.

FIG. 6 illustrates an example of the extraction of a rising point ofinflection based on a signal strength distribution of an access pointover time. As shown in FIG. 6, when the signal strength of the accesspoint is arranged in the order of time, points A and C are where thesignal strength rises and reaches the highest, and thus, are extractedas rising points of inflection.

When the rising points of inflection are extracted, the imaginarylocation coordinate determining unit 1130 calculates a barycentriccoordinate of collection location coordinates of the rising points ofinflection, that is, collection location coordinates where the signalstrength of the rising points of inflection is collected, determines thecalculated barycentric coordinate as an imaginary location coordinate ofthe specific access point, and stores the imaginary location coordinatein the access point information DB 270. Here, the barycentric coordinatemay be replaced by the incenter, the circumcenter, and the like.

Accordingly, an actual location coordinate or an imaginary locationcoordinate of each access point is stored in the access pointinformation DB 270.

The location information request receiving unit 1150 receives a locationmeasurement request for a specific communication terminal. The locationmeasurement request may be received from another communication networkequipment by the request of another communication terminal. When thelocation information request receiving unit 1150 receives the locationmeasurement request, the location information request receiving unit1050 controls the specific communication terminal so as to receiveidentity information (for example, MAC address or SSID) and signalstrength of nearby access points from the specific communicationterminal.

The access point selecting unit 1170 selects R access points among thenearby access points, of which information is received by the locationinformation request receiving unit 1150. Here, R is preferably L^(i)where L is a natural number of 3 or more and ‘i’ is a natural number of2 or more.

When selecting R access points, the access point selecting unit 1170first selects access points having an actual location coordinate byreferring to the access point information DB 270, and then selects theother access points having a high signal strength.

Accordingly, when there are R access points having an actual locationcoordinate, only access points having an actual location coordinate areselected, and if insufficient, access points having a high signalstrength (the signal strength is a value detected and reported by thespecific communication terminal) are selected. In this instance, whenselecting access points having an actual location coordinate, onlyaccess points having a predetermined signal strength or higher may beselected. Here, the signal strength is that of nearby access pointsreceived by the location information request receiving unit 1150 fromthe specific communication terminal.

The location calculating unit 1190 extracts location coordinates of theaccess points selected by the access point selecting unit 1170 from theaccess point information DB 270, and calculates a final one locationcoordinate using the extracted location coordinates by the barycentricmethod.

Specifically, for access points having an actual location coordinate,the location calculating unit 1190 extracts their actual locationcoordinates from the access point information DB 270.

For access points not having an actual location coordinate, the locationcalculating unit 1190 checks whether their imaginary locationcoordinates are stored in the access point information DB 270, and ifso, extracts the imaginary location coordinates from the access pointinformation DB 270.

For access points not having an actual location coordinate and animaginary location coordinate, the location calculating unit 1190extracts collection location coordinates of the top ‘i’ (i′ is thenumber of access points) access points having high signal strength basedon signal strength for location of the corresponding access pointsdetected at each collection location, as location coordinates of thecorresponding access points.

For example, when there are three access points not having an actuallocation coordinate and an imaginary location coordinate, in which thesignal strength for location of an access point A is −40 dB and −50 dB,that of an access point B is −50 dB, −60 dB, and −70 dB, and that of anaccess point C is −60 dB and −100 dB, the top three signal strengths are−40 dB and −50 dB of the access point A and −50 dB of the access pointB. The location calculating unit 1190 extracts collection locationcoordinates where −40 dB and −50 dB of the access point A and −50 dB ofthe access point B are collected, as location coordinates of the accesspoints not having an actual location coordinate and an imaginarylocation coordinate.

The location calculating unit 1190 groups the access points selected bythe access point selecting unit 1170 into a predetermined number ofgroups, in which M (M is a natural number of 3 or more, and ispreferably equal to L) access points are randomly selected in eachgroup, and calculates a barycentric coordinate of each group using theextracted location coordinates of the access points. In this instance,the location calculating unit 1190 equally distributes the access pointshaving an actual location coordinate to each group.

Also, the location calculating unit 1190 groups the calculatedbarycentric coordinates into a predetermined number of groups, in whichM barycentric coordinates are randomly selected in each group, andre-calculates a barycentric coordinate of each group. The locationcalculating unit 1190 repeats this process until one barycentriccoordinate is obtained, and determines the obtained one barycentriccoordinate as a final location of the specific communication terminal.In this instance, when GPS location information is received from thecommunication terminal, the determined barycentric coordinate iscorrected using the GPS location information.

When the location calculating unit 1190 corrects the location coordinateusing the GPS location information, the location calculating unit 1190corrects the location coordinate based on the number of access points.FIG. 12 illustrates an example of a location correction ratio. As shownin FIG. 12, the larger the number of access points used for locationmeasurement or the higher the precision of the GPS location information,the more the location coordinate calculated using the access points iscorrected towards the GPS location coordinate. For example, when thenumber of access points is nine and the precision of the GPS is 35meters or more, a correction ratio is 1:2. That is, a location where astraight line connecting the location coordinate calculated in S709 orS711 and the GPS location coordinate is divided into 1:2 is determinedas a final location coordinate.

When the location calculating unit 1190 calculates a barycentriccoordinate by grouping, if a number X (M<X<2×M) of barycentriccoordinates remain at the end, the location calculating unit 1190 maycalculate one final barycentric coordinate by forming a polygon havingthe number X (M<X<2×M) of barycentric coordinates as the apices.

Alternatively, the location calculating unit 1190 may calculate onefinal barycentric coordinate by grouping barycentric coordinates into apredetermined number of groups, in which the number of barycentriccoordinates in each group is not equal.

When the number of nearby access points is one, the location calculatingunit 1190 may determine an actual location coordinate or imaginarylocation coordinate of the corresponding access point as a locationcoordinate of the specific communication terminal, and may correct thedetermined location coordinate based on the GPS location information.

Additionally, the location calculating unit 1190 may calculate anallowable error radius after measuring a final location coordinate. Thatis, the location calculating unit 1190 may calculate an allowable errorradius relative to the final location coordinate. Specifically, thelocation calculating unit 1190 calculates an allowable error radiusbased on an average of the signal strength of access points used forlocation measurement and whether the GPS location coordinate isreflected.

The final coordinate calculated by the location calculating unit 1190 istransmitted to an object that have requested location measurement.

The access point described in the exemplary embodiment may be called amicro base station, a pico base station, a UbiCell base station, and thelike, depending on the policies of manufacturers or communicationproviders. Accordingly, it should be understood that the access point ofthe exemplary embodiment is a gateway point capable of providing anInternet service to a communication terminal through a common Internetline by directly communicating with the communication terminal via localarea communications.

Also, it is obvious that the location measuring method of the exemplaryembodiment may be applied indoors as well as outdoors. In this instance,while a latitude/longitude coordinate is used as a collection locationcoordinate outdoors, an imaginary location coordinate may be used as acollection location coordinate indoors. For example, the locationmeasuring method of the exemplary embodiment may measure a location of acommunication terminal using the barycentric method by setting imaginarylocation coordinates on each floor of a building classified bycoordinates and collecting information of access points at eachcoordinate.

The method of the exemplary embodiment may be recorded ascomputer-readable program codes in non-transitory computer-readablemedia (CD ROM, random access memory (RAM), read-only memory (ROM),floppy disks, hard disks, magneto-optical disks, and the like) includingprogram instructions to implement various operations embodied by acomputer. Alternatively, the computer-readable media may be atransmission media as carrier waves or signals for transmission over anetwork, such as the Internet.

The apparatuses of the exemplary embodiments, for example the locationmeasuring server 250, may include a bus coupled to every unit of theapparatus, at least one processor (e.g., central processing unit,microprocessor, etc.) that is connected to the bus for controlling theoperations of the apparatuses to implement the above-described functionsand executing commands, and a memory connected to the bus to store thecommands, received messages, and generated messages. The access pointinformation DB 270 may be embodied as a database stored in a memory.

While this specification contains many features, the features should notbe construed as limitations on the scope of the disclosure or of theappended claims. Certain features described in the context of separateexemplary embodiments can also be implemented in combination.Conversely, various features described in the context of a singleexemplary embodiment can also be implemented in multiple exemplaryembodiments separately or in any suitable subcombination.

Although the drawings describe the operations in a specific order, oneshould not interpret that the operations are performed in a specificorder as shown in the drawings or successively performed in a continuousorder, or all the operations are performed to obtain a desired result.Multitasking or parallel processing may be advantageous under anyenvironment. Also, it should be understood that all exemplarilyembodiments do not require the distinction of various system componentsmade in one exemplary embodiment. The program components and systems maybe generally implemented as a single software product or multiplesoftware product packages.

A number of examples have been described above. Nevertheless, it will beunderstood that various modifications may be made. For example, suitableresults may be achieved if the described techniques are performed in adifferent order and/or if components in a described system,architecture, device, or circuit are combined in a different mannerand/or replaced or supplemented by other components or theirequivalents. Accordingly, other implementations are within the scope ofthe following claims.

The invention claimed is:
 1. A method of measuring a location of acommunication terminal, the method comprising: storing locationcoordinates of a plurality of access points in a storage unit; receivingfrom the communication terminal global positioning system (GPS) locationinformation of the communication terminal; extracting the locationcoordinates from the storage unit; calculating the location of thecommunication terminal using the extracted location coordinates; andcorrecting the calculated location using the GPS location information,as a final location coordinate of the communication terminal, whereinthe correcting comprises: selecting a correction ratio based on a numberof the plurality of access points; and determining, as the finallocation coordinate of the communication terminal, a location betweenthe GPS location information and the calculated location according tothe correction ratio.
 2. The method according to claim 1, wherein theselecting of the correction ratio comprises selecting the correctionratio based on the number of the plurality of access points and aprecision of the GPS location information.
 3. The method according toclaim 1, further comprising: receiving from the communication terminalsignal strengths of signals received by the communication terminal fromthe plurality of access points; calculating an error radius based on anaverage of the signal strengths.
 4. A method of measuring a location ofa communication terminal, the method comprising: storing locationcoordinates of a plurality of access points in a storage unit; receivingfrom the communication terminal global positioning system (GPS) locationinformation of the communication terminal; extracting the locationcoordinates from the storage unit; calculating the location of thecommunication terminal using the extracted location coordinates; andcorrecting the calculated location using the GPS location information,as a final location coordinate of the communication terminal, whereinthe calculating comprises: selecting from among the plurality of accesspoints nearby access points nearest to the communication terminal basedon the location coordinates stored in the storage unit and the GPSlocation information of the communication terminal; extracting alocation coordinates of the nearby access points from the storage unit;calculating a barycentric coordinate using the extracted locationcoordinates of the nearby access points; and determining the calculatedbarycentric coordinate as the location of the communication terminal. 5.The method according to claim 4, wherein the calculating of thebarycentric coordinate comprises: grouping the location coordinates ofthe nearby access points; calculating a barycentric coordinate of eachof the groups of location coordinates; and grouping the calculatedbarycentric coordinates and calculating a barycentric coordinate of eachgroup of the calculated barycentric coordinates.
 6. A method ofmeasuring a location of a communication terminal, the method comprising:storing location coordinates of a plurality of access points in astorage unit; receiving from the communication terminal globalpositioning system (GPS) location information of the communicationterminal; extracting the location coordinates from the storage unit;calculating the location of the communication terminal using theextracted location coordinates; and correcting the calculated locationusing the GPS location information, as a final location coordinate ofthe communication terminal, wherein the storing comprises: storing firstlocation coordinates of first access points among the plurality ofaccess points at which the first access points are located; estimatingsecond location coordinates of second access points among the pluralityof access points; and setting the GPS location information of thecommunication terminal as third location coordinates of third accesspoints among the plurality of access points.
 7. The method according toclaim 6, wherein the setting comprises setting for each of the thirdaccess points a collection location coordinate at which a highest signalstrength is received from the third access points by the communicationterminal.
 8. A method of measuring a location of a communicationterminal, the method comprising; storing location coordinates of aplurality of access points in a storage unit; receiving from thecommunication terminal global positioning system (GPS) locationinformation of the communication terminal; extracting the locationcoordinates from the storage unit; calculating the location of thecommunication terminal using the extracted location coordinates; andcorrecting the calculated location using the GPS location information,as a final location coordinate of the communication terminal, whereinthe storing comprises: collecting strengths of signals received by thecommunication terminal from the plurality of access points; extractingrising points of inflection of the strengths of signals by analyzingchanges in the signal strengths for the plurality of access points; anddetermining estimated location coordinates of the plurality of accesspoints based on the extracted rising points of inflection, and storingthe determined estimated location coordinates in the storage unit as thelocation coordinates of the plurality of access points.
 9. The methodaccording to claim 8, wherein the calculating comprises calculating thelocation coordinate of the communication terminal using the estimatedlocation coordinates of the plurality of access points.
 10. An apparatusfor measuring a location of a communication terminal, the apparatuscomprising: a storage unit that stores location coordinates of aplurality of access points; a receiver that receives from thecommunication terminal global positioning system (GPS) locationinformation of the communication terminal; and a location determiningunit that extracts the location coordinates from the storage unit,calculates the location of the communication terminal using theextracted location coordinates, and corrects the calculated locationusing the GPS location information as a final location coordinate of thecommunication terminal, wherein the location determining unitdetermines, as the final location coordinate of the communicationterminal, a location between the GPS location information and thecalculated location according to correction ratio determined based on anumber of the plurality of access points.
 11. The apparatus according toclaim 10, wherein the location determining unit determines thecorrection ratio based on the number of the plurality of access pointsand a precision of the GPS location information.
 12. The apparatusaccording to claim 10, wherein the location determining unit furthercalculates an allowable error radius based on an average of signalstrengths of signals received by the communication terminal from theplurality of access points.
 13. An apparatus for measuring a location ofa communication terminal, the apparatus comprising: a storage unit thatstores location coordinates of a plurality of access points; a receiverthat receives from the communication terminal global positioning system(GPS) location information of the communication terminal; and a locationdetermining unit that extracts the location coordinates from the storageunit, calculates the location of the communication terminal using theextracted location coordinates, and corrects the calculated locationusing the GPS location information as a final location coordinate of thecommunication terminal, wherein the location determining unit calculatesa barycentric coordinate using the location coordinates, and determinesthe calculated barycentric coordinate as the location coordinate of thecommunication terminal.
 14. The apparatus according to claim 13, whereinthe location determining unit groups the extracted location coordinates,calculates a barycentric coordinate of each of the groups of locationcoordinates, groups the calculated barycentric coordinates, andcalculates a barycentric coordinate of each group of the calculatedbarycentric coordinates.
 15. An apparatus for measuring a location of acommunication terminal, the apparatus comprising: a storage unit thatstores location coordinates of a plurality of access points; a receiverthat receives from the communication terminal global positioning system(GPS) location information of the communication; and a locationdetermining unit that extracts the location coordinates from the storageunit, calculates the location of the communication terminal using theextracted location coordinates, and corrects the calculated locationusing the GPS location information as a final location coordinate of thecommunication terminal, wherein the location determining unit storesfirst location coordinates of first access points among the plurality ofaccess points, estimates second location coordinates of second accesspoints among the plurality of access points, and sets the GPS locationinformation of the communication terminal as third location coordinatesof third access points among the plurality of access points.
 16. Theapparatus according to claim 15, wherein the location determining unitsets for each of the third access points a collection locationcoordinate at which a highest signal strength is received from the thirdaccess points by the communication terminal.
 17. An apparatus formeasuring a location of a communication terminal, the apparatuscomprising: a storage unit that stores location coordinates of aplurality of access points; a receiver that receives from thecommunication terminal global positioning system (GPS) locationinformation of the communication terminal; a location determining unitthat extracts the location coordinates from the storage unit, calculatesthe location of the communication terminal using the extracted locationcoordinates, and corrects the calculated location using the GPS locationinformation as a final location coordinate of the communicationterminal; a collector that collects strengths of signals received by thecommunication terminal from the plurality of access points; and anestimator that extracts rising points of inflection of the strengths ofsignals by analyzing changes in the signal strengths for the pluralityof access points, and determines estimated location coordinates of theplurality of access points based on the extracted rising points ofinflection, and stores the estimated location coordinates in the storageunit as the location coordinates of the plurality of access points.